Various systems and methods exist for locating the position of a person by determining the location of a mobile device carried by the person, such as a mobile phone. The most commonly used position location systems employ a Global Positioning System (GPS) and/or triangulation using cellular phone towers. The location of the mobile phone can be displayed to the user, such as by showing the location on a map which is displayed on the mobile phone, can be used by a mobile phone application, such as by associating the current location with a photograph taken with a camera on the mobile phone, and/or can be transmitted over a cellular or wireless network to a remote location, such as a social media network or emergency response service.
The above-described position location systems typically work very well outdoors but encounter problems when the user is inside a building or other structure. To remedy this situation, a variety of indoor position location systems have been developed. Many of these systems use a wireless network, such as a standard network using an IEEE 802.11 wireless protocol, commonly referred to as Wireless LAN or Wi-Fi. These location systems often use multiple antennas or routers and determine a user's location utilizing various triangulation techniques involving the timing and or signal strength of multiple wireless signals. Despite the complexity of these systems, many suffer from reliability problems associated with signal blockage and or reflection problems created by obstacles located in the building. Other existing indoor systems that use Bluetooth or audible signals encounter similar drawbacks.
What is needed but not provided by the prior art are simple yet reliable systems and methods for determining the location of multiple users, particularly in an indoor setting.